1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a structure of a high color gamut liquid crystal display module.
2. The Related Arts
Liquid crystal displays (LCDs) have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus of wide applications, such as liquid crystal televisions, mobile phones, personal digital assistants (PDAs), digital cameras, computer monitors, and notebook computer screens.
Most of the liquid crystal displays that are available in the market are backlighting liquid crystal displays, which generally comprise an enclosure, a liquid crystal panel arranged in the enclosure, and a backlight module mounted in the enclosure.
The liquid crystal panel is structurally made up of a color filter (CF) substrate, a thin-film transistor (TFT) array substrate, and a liquid crystal layer arranged between the two substrates, of which the principle of operation is to control the rotation of the liquid crystal molecules of the liquid crystal layer by application of a driving voltage to the two glass substrates in order to refract out the light emitting from the backlight module to generate an image.
The backlight modules can be classified in two types, namely a side-edge backlight module and a direct backlight module, according to the site where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the backside of the liquid crystal panel to directly form a planar light source supplied to the liquid crystal panel. The side-edge backlight module comprises an LED light bar, serving as a backlight source, which is arranged at an edge of a backplane to be located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face at one side of the light guide plate and is projected out of a light emergence face of the light guide plate, after being reflected and diffused, to pass through an optic film assembly so as to form a planar light source for the liquid crystal panel.
Recently, due to the rapid development of the organic light emitting display (OLED) technology, the LCDs are facing a variety of challenges. Compared to the OLEDs, the LDCs show weakness in various aspects, including device thinning, surface curving, and color saturation. To achieve high color saturation of the LCDs and provide the liquid crystal display modules with high color gamut, such purposes are achieved in the known techniques by adjusting the CF or adopting high color saturation LED backlight source (such as LEDs that comprise red and green fluorescent powders or LEDs that comprise multiple color chips.
Theoretically, one way to achieve high color saturation is to expand the triangular area defined by the color points of the pure colors of the three primary colors, namely red (R), green (G), and blue (B), as large as possible in a CIE (the International Commission on Illumination) chromaticity diagram in order to obtain an enlarged NTSC (National Television System Committee) area. Referring to FIG. 9, the NTSC color saturation of currently common liquid crystal display modules is 72%. To enlarge the area defined by the R, G, and B color points of a liquid crystal display module, one way is to increase the thickness of the CF in order to reduce the half peak widths of the R, G, and B spectrums and another way is to optimize the wavelengths of the R, G, and B spectrums by adjusting the light source so as to make the R wavelength that corresponds to the peak longer, the G wavelength closer to 520 nm, and the B wavelength shorter and simultaneously reduce the half peak widths of the R, G, and B spectrums. Referring to FIG. 1, the half peak widths of R, G, and B of the CF spectrums of the commonly used liquid crystal display modules are relatively wide and overlapping occurs among the colors. Referring to FIG. 2, when light emitting from a white LED passes through the backlight module to be projected out of the CF, the spectrums of the pure colors of the three primary colors, R, G, and B, obtained with the liquid crystal display module are generally not ideal and are affected by the characteristic of the CF so as to show a tailing phenomenon of the spectrums of the three primary colors, R, G, and B, leading to increased half peak widths, reduced color purities, and inward contraction of the corresponding color points in the CIE diagram, making it opposite to the expectation of high color saturation.